This invention relates to the combination of a sulfur compound and specific phosphorus compounds. The invention also relates to lubricating compositions, concentrates and grease containing the combination.
Lubricating compositions are used to prevent damage to machinery under operating conditions. Especially under boundary lubrication conditions, a lubricant must act to minimize harmful metal-to-metal contact. Often additives are useful at providing protection under boundary lubricating condition but sometimes these additive adversely affect other performance characteristics. For instance, a lubricant must still provide protection under high speed, shock loading condition, while not be corrosive to copper and other soft metals.
It is desirable to have a combination of additives which provide extreme pressure protection with out sacrificing other performance characteristics. A combination of additives is desired which will provide good extreme pressure properties to lubricants, which maintain the other parameters required of industry standards, such as API GL-5 and MIL-L2105D gear lubricant requirements.
This invention relates to a lubricating composition comprising a major amount of an oil of lubricating viscosity and (a) a extreme pressure improving amount of at least one sulfur compound, and an antiwear or an extreme pressure improving amount of the combination of (b) at least one ammonium salt of a phosphoric acid ester, (c) at least one phosphite, and (d) at least one thiophosphate or at least one reaction product of a phosphite and sulfur or a source of sulfur. The invention also relates to concentrates and greases containing the combination of the sulfur compound and the specific phosphorus compounds.
The term xe2x80x9chydrocarbylxe2x80x9d includes hydrocarbon as well as substantially hydrocarbon groups. Substantially hydrocarbon describes groups which contain heteroatom substituents that do not alter the predominantly hydrocarbon nature of the substituent. Examples of hydrocarbyl groups include the following:
(1) hydrocarbon substituents, i.e., aliphatic (e.g., alkyl or alkenyl) and alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, aromatic-, aliphatic- and alicyclic-substituted aromatic substituents and the like as well as cyclic substituents wherein the ring is completed through another portion of the molecule (that is, for example, any two indicated substituents may together form an alicyclic radical);
(2) substituted hydrocarbon substituents, i.e., those substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent; those skilled in the art will be aware of such groups (e.g., halo (especially chloro and fluoro), hydroxy, mercapto, nitro, nitroso, sulfoxy, etc.);
(3) heteroatom substituents, i.e., substituents which will, while having a predominantly hydrocarbon character within the context of this invention, contain an atom other than carbon present in a ring or chain otherwise composed of carbon atoms (e.g., alkoxy or alkylthio). Suitable heteroatoms will be apparent to those of ordinary skill in the art and include, for example, sulfur, oxygen, nitrogen and such substituents as, e.g. pyridyl, furyl, thienyl, imidazolyl, etc.
In general, no more than about 2, preferably no more than one heteroatom substituent will be present for every ten carbon atoms in the hydrocarbyl group. Typically, there will be no such heteroatom substituents in the hydrocarbyl group. Therefore, the hydrocarbyl group is hydrocarbon.
As described above the lubricating compositions, concentrates, and grease contain a combination of (a) at least one sulfur compound and at least one mixture comprising (b) an ammonium salt of a phosphoric acid ester, (c) a phosphite, and (d) a thiophosphate or a reaction product of a phosphite and sulfur or a source of sulfur. In one embodiment, the sulfur compound (a) is present at concentrations in the range from about 0.1% to about 10% by weight, or preferably from about 0.2% up to about 8%, or more preferably from about 0.3% up to about 7%, more preferably from about 0.5% to about 5% by weight. Here, as well as elsewhere in the specification and claims, the range and ratio limits may be combined.
Sulfur Compounds
The sulfur compounds include mono- or polysulfide compositions, or mixtures thereof. The sulfur compounds are generally characterized as having sulfide linkages containing an average from 1 up to about 10, or from about 2 up to about 8, or from about 3 up to about 4 sulfur atoms. In one embodiment, the sulfur compound is a mixture of di-, tri- or tetrasulfide materials, preferably having a majority of trisulfide. Materials having at least 70% trisulfide are preferred, with materials containing greater than 80% trisulfide more preferred.
In one embodiment, the sulfur compound is prepared by sulfurizing unsaturated compounds. Materials which may be sulfurized include oils, unsaturated fatty acids, unsaturated fatty esters, olefins, terpenes, or Diels-Alder adducts. Oils which may be sulfurized are natural or synthetic oils, including mineral oils, lard oil, carboxylic acid esters derived from aliphatic alcohols and fatty acids or aliphatic carboxylic acids (e.g., myristyl oleate and oleyl oleate), and synthetic sperm whale oil substitutes and synthetic unsaturated esters or glycerides.
The unsaturated fatty acids generally contain from about 8 to about 30, or from about 12 to about 24 carbon atoms. Examples of unsaturated fatty acids include palmitoleic acid, oleic, linoleic, linolenic, erucic acid, lard oil acid, soybean oil acid, tall oil and rosin acid.
The unsaturated fatty esters include fatty oils, that is, naturally occurring or synthetic esters of glycerol and one or more of the above fatty acids. Examples of fatty esters include animal fats, such as Neat""s-foot oil, lard oil, depot fat, beef tallow, and vegetable oils, including cottonseed oil, corn oil, safflower oil, sesame oil, soybean oil, and sunflower seed oil. The unsaturated fatty esters also may be prepared by esterifying alcohols and polyols with a fatty acid. The alcohols include the above described mono- and polyhydric alcohols, such as methanol, ethanol, propanol, butanol, ethylene glycol, neopentyl glycol, and glycerol.
The olefins, which may be sulfurized, contain at least one olefinic double bond, which is defined as a non-aromatic double bond. In its broadest sense, the olefin may be defined by the formula R*1R*2Cxe2x95x90CR*3R*4, wherein each of R*l, R*, R*3, and R*4 is hydrogen, or an hydrocarbyl group. In general, the R* groups in the above formula which are not hydrogen may be represented by xe2x80x94(CH2)nxe2x80x94A, wherein n is a number from 0 to about 10 and A is represented by xe2x80x94C(R*5)3, xe2x80x94COOR*5, xe2x80x94CON(R*5)2, xe2x80x94COON(R*5)4, xe2x80x94COOM, xe2x80x94CN, xe2x80x94X, xe2x80x94YR*5 or xe2x80x94Ar, wherein: each R*5 is independently hydrogen, or a hydrocarbyl group, with the proviso that any two R*5 groups may be connected to form a ring of up to about 12 carbon atoms; M is one equivalent of a metal cation (preferably Group I or II, e.g., sodium, potassium, barium, or calcium); X is halogen (e.g., chloro, bromo, or iodo); Y is oxygen or divalent sulfur; Ar is an aromatic group of up to about 12 carbon atoms.
The olefinic compound is usually one in which each R group which is not hydrogen is independently alkyl, alkenyl or aryl group, preferably an alkyl group. In one embodiment, R*3 and R*4 are hydrogen and R*1 and R*2 are alkyl or aryl, especially alkyl, having from 1 up to about 30, or from 1 up to about 16, or from 1 up to about 8 carbon atoms. Olefins having from 2 up to about 30, or from about 3 up to about 16 (most often less than about 9) carbon atoms are particularly useful. Olefins having from 2 up to about 8, or from 2 up to about 4 carbon atoms are particularly useful. Isobutene, propylene and their dimers, trimers and tetramers, and mixtures thereof are especially preferred olefins. Of these compounds, isobutylene and diisobutylene are particularly desirable. In one embodiment, the organic polysulfides may be a mixture of di-, tri-, or tetrasulfide materials, preferably having a majority of trisulfide. Materials having at least 70% trisulfide are preferred, with materials containing greater than 80% trisulfide more preferred.
In another embodiment, the organic polysulfide comprise sulfurized olefins prepared by the sulfochlorination of olefins containing four or more carbon atoms and further treatment with inorganic sulfides according to U.S. Pat. No. 2,708,199.
In one embodiment, the sulfurized olefins may be produced by (1) reacting sulfur monochloride with a stoichiometric excess of a lower olefin, e.g. containing two to about seven carbon atoms, (2) treating the resulting product with an alkali metal sulfide in the presence of free sulfur in a mole ratio of no less than 2:1 in an alcohol-water solvent, and (3) reacting that product with an inorganic base. This procedure is described in U.S. Pat. No. 3,471,404, and the disclosure of U.S. Pat. No. 3,471,404 is hereby incorporated by reference for its discussion of this procedure for preparing sulfurized olefins and the sulfurized olefins thus produced. Generally, the olefin reactant contains from about 2 to about 5 carbon atoms and examples include ethylene, propylene, butylene, isobutylene, amylene, etc.
The organic polysulfide may also be the reaction product of a hydrocarbyl mercaptan, sulfur and an olefin. The mercaptans used to make the polysulfide may be hydrocarbyl mercaptans, such as those represented by the formula Rxe2x80x94Sxe2x80x94H, wherein R is a hydrocarbyl group as defined above. In one embodiment, R is an xe2x80x94alkyl, an alkenyl, cycloalkyl, or cycloalkenyl group. R may also be a haloalkyl, hydoxyalkyl, or hydroxyalkyl substituted (e.g. hydroxymethyl, hydroxyethyl, etc.) aliphatic groups. R generally contains from about 2 to about 30 carbon atoms, preferably from about 2 to about 24, more preferably from about 3 to about 18 carbon atoms. Examples include butyl mercaptan, amyl mercaptan, hexyl mercaptan, octyl mercaptan, 6-bydroxymethyl-octanethiol, nonyl mercaptan, decyl mercaptan, 10-amino-dodecanethiol, dodecyl mercaptan, 10-hydroxymethyl-tetradecanethiol, and tetradecyl mercaptan.
The sulfurized olefin may also be prepared by reacting, under superatmospheric pressure, the olefin with a mixture of sulfur and hydrogen sulfide in the presence, or absence, of a catalyst, such as an alkyl amine, followed by removal of low boiling materials. The olefins which may be sulfurized, the sulfurized olefin, and methods of preparing the same are described in U.S. Pat. Nos. 4,119,549, 4,199,550, 4,191,659, and 4,344,854. The disclosure of these patents is hereby incorporated by reference for its description of the sulfurized olefins and preparation of the same.
The organic polysulfide generally has hydrocarbyl groups each independently having from about two to about 30, preferably from about two to about 20, and more preferably from about two to about 12. The hydrocarbyl groups may be aromatic or aliphatic, preferably aliphatic. In one embodiment, the hydrocarbyl groups are alkyl groups.
In one embodiment, the sulfur compound contains a mixture comprising at least about 90% dihydrocarbyl trisulfide, from about 0.5% up to about 8% dihydrocarbyl disulfide, and less than about 5% dihydrocarbyl higher polysulfides. Higher polysulfides are defined as containing four or more sulfide linkages. In one embodiment, the amount of trisulfide is at least about 92%, or preferably at least about 93%. In another embodiment, the amount of dihydrocarbyl higher polysulfides is less than 4%, or preferably less than about 3%. In one embodiment, the dihydrocarbyl disulfide is present in an amount from about 0.5% up to about 5%, or preferably from about 0.6% up to about 3%.
The sulfide analysis is performed on a Varian 6000 Gas Chromatograph and FID detector SP-4100 computing integrator. The Column is a 25 m. Megabore SGE BP-1. The temperature profile is 75xc2x0 C., hold 2 min., to 250xc2x0 C. at 6xc2x0 C./min. The helium flow is 6.0 ml/min plus make-up. The injection temperature is 200xc2x0 C. and the detector temperature is 260xc2x0 C. The injection size is 0.6, ul. References are the monosulfide, disulfide and trisulfide analogues to the sulfur composition for analysis.
The references may be obtainied by fractionating the product to form sulfide fractions (S1, S2 and S3) to be used for analysis. The procedure for analysis is as follows. (1) An area % determination is run on each of the reference samples to determine its purity. (2) An area % determination is run on the sample to be tested to get a general idea of its composition. (3) A calibration blend is accurately weighed based on the area % results of the sample to be tested: then the internal standard toluene, is added to the blend in an amount equal to approximately one-half of the weight of the largest component. (This should give an area approximately the same as that of the largest component.) (4) The weights of each component (i.e., S-1, S-2 and S-3) are corrected by the % purity from step 1. (5) The calibration blend is run in triplicate using the corrected weights and then calculated, using the following formula, to reflect the multiple peaks in S-1 and S-2:       RF    =                            (                      concentration            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢                          components              *                                )                          (                      total            ⁢                          xe2x80x83                        ⁢            area            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            peaks                    )                    ⁢                        (                      area            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            internal            ⁢                          xe2x80x83                        ⁢            standard                    )                          (                      concentration            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            internal            ⁢                          xe2x80x83                        ⁢            standard                    )                                                                           *                    ⁢          Adjusted                ⁢                  xe2x80x83                ⁢        for        ⁢                  xe2x80x83                ⁢        purity        ⁢                  xe2x80x83                ⁢        of        ⁢                  xe2x80x83                ⁢        the        ⁢                  xe2x80x83                ⁢        standard        ⁢                  xe2x80x83                ⁢                  i          .          e          .                      :                          ⁢                  xe2x80x83                ⁢        component        ⁢                  xe2x80x83                ⁢        weight        ⁢                  xe2x80x83                ⁢        times            ⁢              
            ⁢      percent      ⁢              xe2x80x83            ⁢      purity      ⁢              xe2x80x83            ⁢      equals      ⁢              xe2x80x83            ⁢      concentration      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢              component        .              ⁢          xe2x80x83      
(6) These response factors, plus the response factor for the single S-3 peak are used for determining weight percent results for the samples to be tested. (7) Results for S-1 and S-2 are adjusted to include all the peaks attributed to them. (8) Higher polysulfides are determined by difference using the following formula:
S-4=100%xe2x88x92(S-1+S-2+S-3+light ends)
Light ends are defined as any peaks eluded prior to the internal standard.
In one embodiment, the organic polysulfide is prepared as described above using hydrogen sulfide, sulfur, and at least olefin to form an intermediate. The intermediate is fractionally distilled to form the organic polysulfide. In one aspect, the fractional distillation occurs under subatmospheric pressure. Typically the distillation pressure is from about 1 to about 250, preferably from about 1 to about 100, or preferably from about 1 to about 25 mm Hg. A fractionation column, such a Snyder fractionation column may be used. In one embodiment, the fractionation is carried out at a reflux ratio of from about 2:1 up to about 8:1, preferably from about 3:1 up to about 7:1, or preferably from about 4:1 up to about 6:1. S-21.